Novel Solid-State Electrolyte Na3La5Cl18 with High Stability and Fast Ionic Conduction

Motivated by the recent experimental synthesis of a LaCl3-based lithium superionic conductor [Yin, Y.-C. Nature 2023, 616, 77-83], we explore the potential of a LaCl3-based system for a sodium superionic conductor in this work. Using density functional theory combined with molecular dynamics simulation and a grand potential phase diagram analysis, we find that the resulting Na3La5Cl18 exhibits high energetic stability with a small energy-above-hull of 18 meV per atom, a large band gap of 5.58 eV, a wide electrochemical window of 0.41-3.76 V from the cathodic to the anodic limit, and a high Na+ conductivity of 1.3 mS/cm at 300 K. Furthermore, Na3La5Cl18 shows high chemical interface stability with the reported high-potential cathode materials such as NaCoO2, NaCrO2, Na2FePO4F, Na3V2(PO4)3, and Na3V2(PO4)2F3. These findings clearly suggest that the LaCl3-based framework can be used as a building block not only for Li-ion but also for Na-ion batteries.